1. Field of the Invention
The present invention relates to a method and an apparatus for interference control in a wireless communication system with a hierarchical cell layout. More particularly, the present invention relates to a method and an apparatus for, if a femto cell exists within an area of a macro cell, minimizing the interference of the femto cell on the macro cell.
2. Description of the Related Art
In recent years, in a cellular wireless communication system, a femto cell concept has been proposed to address problems resulting from electric wave shadow areas, which can be caused by a movement between Base Stations (BSs) or a poor channel state, while a high-level data service is provided. In contrast with a macro cell, a femto cell has a very small cell area. A plurality of femto cells can be installed within one macro cell area.
The macro cell and femto cell can use the same or different frequency bands. If a macro cell and a femto cell use different frequency bands from each other, interference is generated only by a signal leaked out of a frequency band used by each respective cell. The above generation of interference can be addressed by allocating less power to the femto cell but, because the femto cell is required to use an additional frequency band, there is a problem that efficiency of frequency band use is reduced. However, if the macro cell and femto cell use the same frequency band, there is no need to use an additional frequency band, but much more interference is generated between the macro cell and femto cell.
The conventional art provides a variety of techniques to control interference between cells. For example, there is a Fractional Frequency Reuse (FFR) technique for maintaining efficiency of an entire cell while improving an efficiency of a cell boundary portion. As illustrated in FIG. 1, after dividing a cell area into an internal area and an external area, the FFR technique sets a frequency reuse rate of the cell internal area to ‘1’ and sets a frequency reuse rate of the cell external area to ‘3’, thus allowing orthogonality of a frequency band for an external area of each cell. After dividing a frequency band for the cell external area into three fractional bands, the FFR technique uses the fractional band to take orthogonality in an external area of each cell.
However, the FFR technique is for a horizontal cell layout in which there are horizontally continuous cells of a similar size, and has a problem that it is difficult to be applied to a hierarchical cell layout in which there is the femto cell within the macro cell.